1. Field of the Invention
The present invention relates to a producing method of a semiconductor device and a semiconductor device producing apparatus, and more particularly, to a producing method of a semiconductor device using plasma processing and a semiconductor device producing apparatus using plasma.
2. Description of the Related Art
In producing an MOS-type semiconductor device based on a silicon semiconductor substrate for example, it is necessary to form a gate oxide film comprising a silicon oxide film on a surface of the silicon semiconductor substrate. In producing a thin film transistor (TFT) also, it is necessary to form a gate oxide film on a surface of a silicon layer provided on a transparent glass substrate. This gate oxide film bears the reliability of the semiconductor device, and the silicon oxide film is required to have high dielectric breakdown resistance and long term reliability.
In recent years, in a CMOS transistor, an effort is under way to lower the voltage in order to lower the power consumption. For this purpose, threshold voltage which is symmetric and sufficiently low with respect to a PMOS semiconductor device and an NMOS semiconductor device is required. To meet this requirement, in the PMOS semiconductor device, a gate electrode comprising a poly-silicon layer including p-type impurities is used instead of a conventional gate electrode comprising a poly-silicon layer including n-type impurities. However, generally used boron atom (B) which is p-type impurity atom passes through a gate oxide film from a gate electrode by various thermal processing procedure in semiconductor producing procedure after the gate electrode is formed, and reaches a silicon semiconductor substrate, and adversely varies the threshold voltage of the PMOS semiconductor device.
This phenomenon appears more outstandingly when the gate oxide film is made thin for making a design rule of the semiconductor device finer and for lowering electric power with reduction in power consumption.
In order to restrain the boron atom (B) which is the impurity atom from dispersing into the silicon semiconductor substrate, it is conceived that nitrogen atom should be introduced into the gate oxide film. It is possible to introduce nitrogen atom into a gate insulative film in an ammonia atmosphere at a high temperature using a thermal nitriding method. If this thermal nitriding method is used, however, the nitrogen atom passes through the gate oxide film and enters also into the silicon semiconductor substrate, and lowers the current driving ability of the semiconductor device.
Further, if the forming processing of the gate oxide film and the nitriding processing are carried out in separate processing chambers, since the gate oxide film is exposed to an atmosphere or an atmosphere in a transfer chamber having low degree of vacuum after the gate oxide film is formed, there is an adverse possibility that organic contaminant adheres to a surface of the gate oxide film to deteriorate characteristics of the device.